6711316: Open source the Garbage-First garbage collector

First mercurial integration of the code for the Garbage-First garbage collector.

Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr

hotspot/src/share/vm/gc_implementation/g1/concurrentZFThread.cpp

@@ -0,0 +1,191 @@
+/*
+ * Copyright 2001-2007 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+#include "incls/_precompiled.incl"
+#include "incls/_concurrentZFThread.cpp.incl"
+
+// ======= Concurrent Zero-Fill Thread ========
+
+// The CM thread is created when the G1 garbage collector is used
+
+int ConcurrentZFThread::_region_allocs = 0;
+int ConcurrentZFThread::_sync_zfs = 0;
+int ConcurrentZFThread::_zf_waits = 0;
+int ConcurrentZFThread::_regions_filled = 0;
+
+ConcurrentZFThread::ConcurrentZFThread() :
+  ConcurrentGCThread(),
+  _co_tracker(G1ZFGroup)
+{
+  create_and_start();
+}
+
+void ConcurrentZFThread::wait_for_ZF_completed(HeapRegion* hr) {
+  assert(ZF_mon->owned_by_self(), "Precondition.");
+  note_zf_wait();
+  while (hr->zero_fill_state() == HeapRegion::ZeroFilling) {
+    ZF_mon->wait(Mutex::_no_safepoint_check_flag);
+  }
+}
+
+void ConcurrentZFThread::processHeapRegion(HeapRegion* hr) {
+  assert(!Universe::heap()->is_gc_active(),
+         "This should not happen during GC.");
+  assert(hr != NULL, "Precondition");
+  // These are unlocked reads, but if this test is successful, then no
+  // other thread will attempt this zero filling.  Only a GC thread can
+  // modify the ZF state of a region whose state is zero-filling, and this
+  // should only happen while the ZF thread is locking out GC.
+  if (hr->zero_fill_state() == HeapRegion::ZeroFilling
+      && hr->zero_filler() == Thread::current()) {
+    assert(hr->top() == hr->bottom(), "better be empty!");
+    assert(!hr->isHumongous(), "Only free regions on unclean list.");
+    Copy::fill_to_words(hr->bottom(), hr->capacity()/HeapWordSize);
+    note_region_filled();
+  }
+}
+
+void ConcurrentZFThread::run() {
+  initialize_in_thread();
+  Thread* thr_self = Thread::current();
+  _vtime_start = os::elapsedVTime();
+  wait_for_universe_init();
+  _co_tracker.enable();
+  _co_tracker.start();
+
+  G1CollectedHeap* g1 = G1CollectedHeap::heap();
+  _sts.join();
+  while (!_should_terminate) {
+    _sts.leave();
+
+    {
+      MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);
+
+      // This local variable will hold a region being zero-filled.  This
+      // region will neither be on the unclean or zero-filled lists, and
+      // will not be available for allocation; thus, we might have an
+      // allocation fail, causing a full GC, because of this, but this is a
+      // price we will pay.  (In future, we might want to make the fact
+      // that there's a region being zero-filled apparent to the G1 heap,
+      // which could then wait for it in this extreme case...)
+      HeapRegion* to_fill;
+
+      while (!g1->should_zf()
+             || (to_fill = g1->pop_unclean_region_list_locked()) == NULL)
+        ZF_mon->wait(Mutex::_no_safepoint_check_flag);
+      while (to_fill->zero_fill_state() == HeapRegion::ZeroFilling)
+        ZF_mon->wait(Mutex::_no_safepoint_check_flag);
+
+      // So now to_fill is non-NULL and is not ZeroFilling.  It might be
+      // Allocated or ZeroFilled.  (The latter could happen if this thread
+      // starts the zero-filling of a region, but a GC intervenes and
+      // pushes new regions needing on the front of the filling on the
+      // front of the list.)
+
+      switch (to_fill->zero_fill_state()) {
+      case HeapRegion::Allocated:
+        to_fill = NULL;
+        break;
+
+      case HeapRegion::NotZeroFilled:
+        to_fill->set_zero_fill_in_progress(thr_self);
+
+        ZF_mon->unlock();
+        _sts.join();
+        processHeapRegion(to_fill);
+        _sts.leave();
+        ZF_mon->lock_without_safepoint_check();
+
+        if (to_fill->zero_fill_state() == HeapRegion::ZeroFilling
+            && to_fill->zero_filler() == thr_self) {
+          to_fill->set_zero_fill_complete();
+          (void)g1->put_free_region_on_list_locked(to_fill);
+        }
+        break;
+
+      case HeapRegion::ZeroFilled:
+        (void)g1->put_free_region_on_list_locked(to_fill);
+        break;
+
+      case HeapRegion::ZeroFilling:
+        ShouldNotReachHere();
+        break;
+      }
+    }
+    _vtime_accum = (os::elapsedVTime() - _vtime_start);
+    _sts.join();
+
+    _co_tracker.update();
+  }
+  _co_tracker.update(false);
+  _sts.leave();
+
+  assert(_should_terminate, "just checking");
+  terminate();
+}
+
+bool ConcurrentZFThread::offer_yield() {
+  if (_sts.should_yield()) {
+    _sts.yield("Concurrent ZF");
+    return true;
+  } else {
+    return false;
+  }
+}
+
+void ConcurrentZFThread::stop() {
+  // it is ok to take late safepoints here, if needed
+  MutexLockerEx mu(Terminator_lock);
+  _should_terminate = true;
+  while (!_has_terminated) {
+    Terminator_lock->wait();
+  }
+}
+
+void ConcurrentZFThread::print() {
+  gclog_or_tty->print("\"Concurrent ZF Thread\" ");
+  Thread::print();
+  gclog_or_tty->cr();
+}
+
+
+double ConcurrentZFThread::_vtime_accum;
+
+void ConcurrentZFThread::print_summary_info() {
+  gclog_or_tty->print("\nConcurrent Zero-Filling:\n");
+  gclog_or_tty->print("  Filled %d regions, used %5.2fs.\n",
+                      _regions_filled,
+                      vtime_accum());
+  gclog_or_tty->print("  Of %d region allocs, %d (%5.2f%%) required sync ZF,\n",
+                      _region_allocs, _sync_zfs,
+                      (_region_allocs > 0 ?
+                       (float)_sync_zfs/(float)_region_allocs*100.0 :
+                       0.0));
+  gclog_or_tty->print("     and %d (%5.2f%%) required a ZF wait.\n",
+                      _zf_waits,
+                      (_region_allocs > 0 ?
+                       (float)_zf_waits/(float)_region_allocs*100.0 :
+                       0.0));
+
+}